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COMBINATORICS
2004
13 years 9 months ago
2004
We present a class of permutations for which the number of distinctly ordered subsequences of each permutation approaches an almost optimal value as the length of the permutation ...
COMBINATORICS
2004
13 years 9 months ago
2004
An antichain is a collection of sets in which no two sets are comparable under set inclusion. An antichain A is flat if there exists an integer k 0 such that every
COMBINATORICS
2004
13 years 9 months ago
2004
We gave a new criterion for graphical partitions. We derive a new recursion formula, which allows the computation of the number g(n) of graphical partitions of weight n for up to ...
COMBINATORICS
2004
13 years 9 months ago
2004
We prove Borchardt's identity det 1 xi - yj per 1 xi - yj = det 1 (xi - yj)2 by means of sign-reversing involutions.
COMBINATORICS
2004
13 years 9 months ago
2004
Given a sequence {Qn(x)} n=0 of symmetric orthogonal polynomials, defined by a recurrence formula Qn(x) = n